Conventional foot mounted articles for effecting movement through fluid media. e.g., fins for swimming through water, generally take the form of fins which comprise a blade constructed of a relatively rigid material connected at the rear to a shoe made of a relatively yielding material. As set forth in the present description, the term “relatively rigid material” refers to a material such as, for example, polypropylene or the equivalent, while the term “relatively yielding material” in the present description refers to a material such as a thermoplastic polymer based essentially on SEBS elastomers or the equivalent.
Such materials are commonly used in the production of fins for swimmers.
In order to protect against scratches and cuts that may result when the fin comes into contact with reefs, stones and the like, longitudinal edges of the blade are often lined with a yielding material like that of the material comprising the shoe. More particularly, such lining is formed in lateral ribs that generally extend both above and below the plane of the blade so as to improve the propulsive efficacy of the fin without increasing the overall rigidity of the blade. According to a previous invention of the same applicant, these ribs may be constructed of a material having a rigidity intermediate between that of the shoe and the blade. In this manner, the designer has much more freedom of choice in the hydrodynamic and mechanical characteristics of the fin, which are often in contrast with each other.
Generally speaking, the efficiency of a fin depends on the above-mentioned characteristics. Accordingly, designers and manufacturers of fins concentrate on them, though not without considering that any modification to the structure of the fin that is intended to improve these characteristics must also be aesthetically pleasing as well as original.
More particularly, it has been found that the efficiency of a conventional swimming fin has a first limitation in that the rigid blade generally bends only in a plane substantially at right angles to the plane of the undeformed blade, its transverse sections being maintained substantially constant.
Second, it has been found, from a hydrodynamic point of view, that the fin's efficiency is to some extent negatively affected by the presence of buckles on the closing strap of the shoe. This is because the buckles typically project sideways and are thus an obstacle to the free flow of water along the fin.